Provision of a method of improving preservation stabilityof glutathione in a solid composition containing glutathione andarginine, or a solid composition containing glutathione andarginine, which shows improved preservation stability ofglutathione.In the production of a solid composition containingglutathione and arginine, glutathione and arginine are made tobe coexistent with an organic acid. Examples of the organic acidinclude citric acid, tartaric acid, ascorbic acid, malic acid,malonic acid, succinic acid, fumaric acid, maleic acid and thelike. The amount of the organic acid to be coexistent withglutathione and arginine is generally 0.1 - 2 parts by weightrelative to 1 part by weight of arginine.
